1. Field of the Invention
The present invention relates generally to electrophotographic printing devices and, more particularly, to drive systems for the fuser units of electrophotographic printing devices.
2. Description of the Related Art
In the electrophotographic (EP) imaging process used in printers, copiers and the like, a photosensitive member, such as a photoconductive drum or belt, is uniformly charged over an outer surface. An electrostatic latent image is formed by selectively exposing the uniformly charged surface of the photosensitive member. Toner particles are applied to the electrostatic latent image, and thereafter the toner image is transferred to the media intended to receive the final permanent image. The toner image is fixed to the media by the application of heat and pressure in a fuser.
A fuser is known to include a heated roll and a backup roll forming a fuser nip through which the media passes. At least one of the rolls is driven, along with a variety of infeed and outfeed rolls to transport the media to and from the nip. If two-sided printing is provided, a duplexing path to reverse the media also includes driven rolls to transport the media along the duplexing path. A fuser drive system drives the aforementioned rolls, perhaps also together with other fuser components.
Known designs for drive systems of fuser units in electrophotographic printing devices incorporate a portion of the fuser drive system in the machine separate from the fuser unit itself. The machine side of the fuser drive system is known to include a motor and a portion of a drive train, and includes a mounting plate, studs and at least one gear. It is also known to use a belt pulley drive system in a fuser unit drive system. It also is known to use the machine side motor to drive more than just the fuser unit components. For example, the motor may also drive components within the paper path or EP system. The remainder of the fuser drive system is included in the fuser unit, and includes at least one gear of the drive train that engages a gear on the machine side of the drive system.
In a known design, the motor that drives the fuser and other paper feed modules is located on a bracket mounted to the machine frame. A fuser drive gear on the machine side mates with an input gear located on the fuser upon insertion of the fuser unit. Each time the fuser unit is removed and installed, such as for servicing or replacement, the drive system is separated and re-engaged. This making and breaking of the drive train creates design challenges and potential problems such as sub-optimal gear center distance control, which can lead to premature gear wear and noise.
It is known to provide the fuser unit as a customer replaceable unit (CRU) or as a field replaceable unit (FRU) intended to be serviced or replaced by a field technician. With the drive system split between the machine side and the fuser unit side of the device, gear center distance can vary across the module boundaries. Gear life can be shortened and objectionable noise created if the mating gears on the machine side and the fuser unit side are not optimally positioned. Further, during the life of an electrophotographic printer, a fuser unit may be replaced several times. Since the motor and a portion of the drive train are not part of the fuser unit, old components of the drive system remain when the fuser unit is replaced. An old, partially worn gear on the machine side must mate with a new, non-worn gear on the fuser unit. Optimal gear engagement might not result, and increased noise and wear may occur immediately when the new fuser unit is installed.
What is needed in the art is an integrated drive train that is self-contained within the fuser unit, to simplify machine architecture and improve machine performance and reliability.